FafnirSuper-Precision Angular Contact Ball Bearing – Straight Bore, 100 mm ID, 150 mm OD, 24 mm Width, Open, 25° Contact Angle, Medium Preload, Phenolic Cage.

Product Description

What this part is

Fafnir 3MM9120WI-DUM super-precision angular contact ball bearing, 9100 series. Brand: Fafnir (Timken). Part Number: 3MM9120WI-DUM. Bore: 100 mm. Outside Diameter: 150 mm. Overall Width: 24 mm. Design Units: Metric. Number Of Rows: 1. Rolling Elements: Steel ball. Bore Type: Straight. Closure Type: Open. Bearing Material: Chrome bearing steel. Item Weight: 2.50 lbs.

Decoding the designation

Contact Angle: 25°. Precision Class: P4S. Precision Rating: ABEC 7/9. Cage Material: Phenolic. Cage Type: CR – phenolic outer land riding. Preload: Medium. Arrangement / Configuration: Universally ground for duplex mounting. Series: 9100, Fafnir’s designation for the ISO 70xx series — a 9120 carries the 7020 envelope. Timken World Part Number: 7020E-T-P4S-DUM.

Load ratings and speeds

Dynamic Radial Load Rating (C1), per bearing: 79,200 N (17,800 lbf). Dynamic Radial Load Rating (C1 ISO, per row): 71,800 N (16,200 lbf). Static Radial Load Rating (C0), per bearing: 73,400 N (16,500 lbf). Limiting Speed, grease: 8,300 rpm. Limiting Speed, oil: 15,000 rpm.

What these specs mean in practice

A 25° contact angle carries more thrust load and holds the shaft more stiffly along its axis than a 15° bearing on the same envelope. The medium preload class sits between the light class used for maximum speed and the heavy class used for maximum stiffness. The phenolic cage rides on the outer ring land, staying centred at speed and holding lubricant against the ball pockets. Oil feed lifts the speed ceiling from 8,300 to 15,000 rpm. Internal Clearance: N/A — the bearing is set by preload rather than by clearance.

Mounting data

Shaft Backing Shoulder Diameter: 109.9 mm (4.330 in). Housing Backing Shoulder Diameter: 140.8 mm (5.550 in). Maximum Shaft Fillet Radius: 1.5 mm (0.059 in). Outer Ring “To Clear” Radius: 1.5 mm (0.059 in).

Quantity and configuration

Unit Quantity: 1 Pc. Mounting Arrangement: Universal, DUM duplex grind. The faces are ground so that two bearings of this designation stack directly to the medium preload class with no shimming or regrinding, and a single piece runs equally well on its own.

Interchange guidance

Cross-References: SKF 7020 ACD/P4A, FAG B7020-E-T-P4S-UM, NSK 7020A5, Timken 7020E. Each shares the 100 x 150 x 24 mm envelope and the 25° contact angle. Harmonization Code: 8482.10.50.68.

Designation variants

MPN Variants: 3MM9120WI-DUM, 3MM9120WIDUM, 3MM9120WID-UM, 3MM 9120 WI DUM, 3MM-9120-WI-DUM, 3MM9120WICRDUM, 7020E-T-P4S-DUM, 7020A5, 7020ACD, 7020E, 3MM9120WI.